Quasar-Contract

Quasar-Contract is an on-chain part of the Quasar project (see Quasar-EVM repository). Quasar-Contract contract is used to write and read currency prices and used as an price oracle for the rollups.

Table of content

• Deploy and verify
• Usage
• Structs
• Events
• Methods

Deploy and verify

The deployment scripts are configured to interact with rollup chains. Before deploy you need to start new rollup, install all dependencies and set the env variables.

Env variables

Env variable names can be found in the .env.example file. You can copy this file and set needed variables to run the deployment scripts.

Name	Example	Description
RPC	https://jesterfair-rpc.eu-north-2.gateway.fm	Rollup RPC-provider URL
PK		Deployed oracle owner wallet private key
CHAIN_NAME	jesterfair	Rollup chain name
CHAIN_ID	1413045109	Rollup chain ID
BLOCKSCOUT_URL_API	https://jesterfair-blockscout.eu-north-2.gateway.fm/api/	Normally - the same as the Blockscout URL with /api/ at the end
BLOCKSCOUT_URL	https://jesterfair-blockscout.eu-north-2.gateway.fm	Blockcsout web app URL

Install dependencies

To install dependencies run:

yarn install

Deploy

To deploy smart-contract use this command:

yarn hardhat deploy

It will run the deployment and verification scripts. Script will log each step and log the new smart-contract address. Be aware, if you use the Blockscout API, verification may return error, but the verification may be done. It should be checked manually.

Usage

After contract deployment it is assumed that you need to deploy and run the Quasar-EVM oracle. It will listen to the needed currencies and push them to the smart-contract.

Before the quasar-evm is started you need to add all needed currencies to the smart contract using the AddCurrency method.

To get needed currency price onchain use the GetPrice method. Prices are sotred with 5 decimals.

!!! Attention !!!

At the time of writing the Quasar-EVM do not support listening to this smart-contract events. If you add or change existing currencies while the Quasar-EVM is online you will need to restart EVM service manually after all changes are made on-chain.

Structs

Currency

struct Currency {
  string name;
  string symbol;
}

Fields:

• name: ERC-20 token name
• symbol: ERC-20 token Symbol

Events

CurrencyAdded

event CurrencyAdded(uint64 indexed id, string name, string symbol);

• Description: Triggered whenever new currency is updated
• Parameters:
  • id - new currency ID
  • name: ERC-20 token name
  • symbol: ERC-20 token Symbol

CurrencyUpdated

event CurrencyUpdated(uint64 indexed id, string name, string symbol);

• Description: Triggered whenever an existing currency is updated
• Parameters:
  • id - existing currency ID
  • name: ERC-20 token name
  • symbol: ERC-20 token Symbol

PriceUpdated

event PriceUpdated(uint64 indexed id, uint256 price);

• Description: Triggered whenever an existing currency price is updated
• Parameters:
  • id - updated currency ID
  • price: currency price

CurrencyStateChanged

event CurrencyStateChanged(uint64 indexed id, bool state);

• Description: Triggered whenever an existing currency state is changed
• Parameters:
  • id - updated currency ID
  • state: new currency state. True if currency is active and false if not

Methods

GetCurrencyID

function getCurrencyID(string memory symbol) external view returns(uint64, bool);

• Description: Return currency ID and currency state by given symbol. Will return 0 and false if symbol do not exist.
• Parameters:
  • symbol - currency symbol.
• Returns:
  • uint64 - currency ID
  • bool - currency state. True if currency is active and false if not

GetSupportedCurrencies

function getSupportedCurrencies() external view returns(Currency[] memory, bool[] memory);

• Description: Return all existing currencies and states. Will return zero length arrays is no currencies registered in the smart-contract
• Returns:
  • Currency[] - currency struct array
  • bool[] - currency states

GetNextID

function getNextID() external view returns (uint64);

• Description: Return next currency ID. First currency ID is 1. To calculate total currencies in the smart-contract user next currency ID - 1.
• Returns:
  • uint64 - next currency ID

GetPrice

function getPrice(uint64 id) external view returns (uint256);

• Description: Price for given currency ID
• Parameters:
  • id - currency ID
• Returns:
  • uint256 - currency price with 5 decimals

GetCurrencyMetadata

function getCurrencyMetadata(uint64 id) external view returns (Currency memory);

• Description: Get currency metadata
• Parameters:
  • id - currency ID
• Returns:
  • Currency - currency metadata struct

IsCurrencySupported

function isCurrencySupported(uint64 id) external view returns (bool);

• Description: Get currency state. True if supported false if not. If currency do not exist will also return false.
• Parameters:
  • id - currency ID
• Returns:
  • bool - currency state

AddCurrency

function addCurrency(string memory name, string memory symbol) external onlyOwner;

• Description: Add new currency to the smart-contract. Also set the currency state to true.
• Parameters:
  • name - currency name
  • symbol - currency symbol
• Requirements:
  • Caller should be a contract owner
  • Name cannot be blank
  • Symbol cannot be blank
• Emits:
  • CurrencyAdded event.

UpdateCurrency

function updateCurrency(uint64 id, string memory name, string memory symbol) external onlyOwner;

• Description: Updates name and symbol of existing currency.
• Parameters:
  • id - existing currency ID
  • name - new currency name
  • symbol - new currency symbol
• Requirements:
  • Caller should be a contract owner
  • Name cannot be blank
  • Symbol cannot be blank
  • Currency ID should exist
• Emits:
  • CurrencyUpdated event.

PushPrice

function pushPrice(uint64 id, uint256 price) external onlyOwner;

• Description: Updates name and symbol of existing currency.
• Parameters:
  • id - existing currency ID
  • price - new currency price with 5 decimals
• Requirements:
  • Caller should be a contract owner
  • Currency ID should exist
• Emits:
  • PriceUpdated event.

ChangeCurrencyState

function changeCurrencyState(uint64 id, bool state) external onlyOwner;

• Description: Updates name and symbol of existing currency.
• Parameters:
  • id - existing currency ID
  • state - new currency price state
• Requirements:
  • Caller should be a contract owner
  • Currency ID should exist
• Emits:
  • CurrencyStateChanged event.